Prescribing of clozapine and olanzapine: dosage, polypharmacy and patient ethnicity

Involvement of Extracellular Vesicles in the Proinflammatory Response to Clozapine: Implications for Clozapine-Induced Agranulocytosis

Most idiosyncratic drug reactions (IDRs) appear to be immune-mediated, but mechanistic events preceding severe reaction onset remain poorly defined. Damage-associated molecular patterns (DAMPs) may contribute to both innate and adaptive immune phases of IDRs, and changes in extracellular vesicle (EV) cargo have been detected post-exposure to several IDR-associated drugs. To explore the hypothesis that EVs are also a source of DAMPs in the induction of the immune response preceding drug-induced agranulocytosis, the proteome and immunogenicity of clozapine- (agranulocytosis-associated drug) and olanzapine- (non-agranulocytosis-associated drug) exposed EVs were compared in two preclinical models: THP-1 macrophages and Sprague-Dawley rats. Compared with olanzapine, clozapine induced a greater increase in the concentration of EVs enriched from both cell culture media and rat serum. Moreover, treatment of drug-naïve THP-1 cells with clozapine-exposed EVs induced an inflammasome-dependent response, supporting a potential role for EVs in immune activation. Proteomic and bioinformatic analyses demonstrated an increased number of differentially expressed proteins with clozapine that were enriched in pathways related to inflammation, myeloid cell chemotaxis, wounding, transforming growth factor-β signaling, and negative regulation of stimuli response. These data indicate that, although clozapine and olanzapine exposure both alter the protein cargo of EVs, clozapine-exposed EVs carry mediators that exhibit significantly greater immunogenicity. Ultimately, this supports the working hypothesis that drugs associated with a risk of IDRs induce cell stress, release of proinflammatory mediators, and early immune activation that precedes severe reaction onset. Further studies characterizing EVs may elucidate biomarkers that predict IDR risk during development of drug candidates. SIGNIFICANCE STATEMENT: This work demonstrates that clozapine, an idiosyncratic drug-induced agranulocytosis (IDIAG)-associated drug, but not olanzapine, a safer structural analogue, induces an acute proinflammatory response and increases extracellular vesicle (EV) release in two preclinical models. Moreover, clozapine-exposed EVs are more immunogenic, as measured by their ability to activate inflammasomes, and contain more differentially expressed proteins, highlighting a novel role for EVs during the early immune response to clozapine and enhancing our mechanistic understanding of IDIAG and other idiosyncratic reactions.

Infections associated with clozapine: a pharmacovigilance study using VigiBase®

Introduction: Clozapine is primarily reserved for treatment-resistant schizophrenia due to safety concerns associated with its use. Infections have been reported with clozapine, which may lead to elevated serum levels of the drug. However, the existing literature on this topic is limited. Therefore, we conducted a study using VigiBase® to investigate the potential over-reporting of infections associated with clozapine, to explore the presence of dose-dependency, and to investigate the underlying mechanism. Methods: Disproportionality analyses were performed using VigiBase to assess the association between clozapine and all types of infections, the association between clozapine-associated infections and neutropenia, the association between clozapine-associated infections and agranulocytosis, the dose-effect relationship between clozapine and infections, and the interaction between clozapine and the main strong CYP450 inhibitors using reports carried out until 11 April 2023. Results: A statistically significant signal of infections was observed with clozapine, as indicated by an information component of 0.43 [95% CI: (0.41-0.45)]. The most commonly reported infections were respiratory and gastrointestinal in nature. Neutropenia showed weaker association with clozapine-associated reports of infections compared to other clozapine-associated reports [X2 (1, N = 204,073) = 454; p < 0.005], while agranulocytosis demonstrated a stronger association with clozapine-associated reports of infections [X2 (1, N = 204,073) = 56; p < 0.005]. No evidence of dose-dependency was observed. Among the 17 tested CYP inhibitors, significant drug-drug interactions were found with clarithromycin, metronidazole, valproic acid, lansoprazole, omeprazole, amiodarone, and esomeprazole. Discussion: Our study revealed a significant safety signal between clozapine use and infections, predominantly respiratory and gastrointestinal infections. The co-administration of clozapine with valproic acid or proton pump inhibitors may potentially contribute to an increased risk of infection. Further vigilance is warranted in clinical practice, and consideration of therapeutic drug monitoring of clozapine in cases involving concomitant use of these drugs or in the presence of infections may be beneficial.

Unraveling ethnic disparities in antipsychotic prescribing among patients with psychosis: A retrospective cohort study based on electronic clinical records

BACKGROUND

Previous studies have shown mixed evidence on ethnic disparities in antipsychotic prescribing among patients with psychosis in the UK, partly due to small sample sizes. This study aimed to examine the current state of antipsychotic prescription with respect to patient ethnicity among the entire population known to a large UK mental health trust with non-affective psychosis, adjusting for multiple potential risk factors.

METHODS

This retrospective cohort study included all patients (N = 19,291) who were aged 18 years or over at their first diagnoses of non-affective psychosis (identified with the ICD-10 codes of F20-F29) recorded in electronic health records (EHRs) at the South London and Maudsley NHS Trust until March 2021. The most recently recorded antipsychotic treatments and patient attributes were extracted from EHRs, including both structured fields and free-text fields processed using natural language processing applications. Multivariable logistic regression models were used to calculate the odds ratios (OR) for antipsychotic prescription according to patient ethnicity, adjusted for multiple potential contributing factors, including demographic (age and gender), clinical (diagnoses, duration of illness, service use and history of cannabis use), socioeconomic factors (level of deprivation and own-group ethnic density in the area of residence) and temporal changes in clinical guidelines (date of prescription).

RESULTS

The cohort consisted of 43.10 % White, 8.31 % Asian, 40.80 % Black, 2.64 % Mixed, and 5.14 % of patients from Other ethnicity. Among them, 92.62 % had recorded antipsychotic receipt, where 24.05 % for depot antipsychotics and 81.72 % for second-generation antipsychotic (SGA) medications. Most ethnic minority groups were not significantly different from White patients in receiving any antipsychotic. Among those receiving antipsychotic prescribing, Black patients were more likely to be prescribed depot (adjusted OR 1.29, 95 % confidence interval (CI) 1.14-1.47), but less likely to receive SGA (adjusted OR 0.85, 95 % CI 0.74-0.97), olanzapine (OR 0.82, 95 % CI 0.73-0.92) and clozapine (adjusted OR 0.71, 95 % CI 0.6-0.85) than White patients. All the ethnic minority groups were less likely to be prescribed olanzapine than the White group.

CONCLUSIONS

Black patients with psychosis had a distinct pattern in antipsychotic prescription, with less use of SGA, including olanzapine and clozapine, but more use of depot antipsychotics, even when adjusting for the effects of multiple demographic, clinical and socioeconomic factors. Further research is required to understand the sources of these ethnic disparities and eliminate care inequalities.

Haematologic malignancies associated with clozapine v. all other antipsychotic agents: a pharmacovigilance study in VigiBase®

BACKGROUND

Clozapine is mainly used in patients with treatment-resistant schizophrenia and may lead to potentially severe haematologic adverse events, such as agranulocytosis. Whether clozapine might be associated with haematologic malignancies is unknown. We aimed to assess the association between haematologic malignancies and clozapine using Vigibase®, the WHO pharmacovigilance database.

METHODS

We performed a disproportionality analysis to compute reporting odds-ratio adjusted for age, sex and concurrent reporting of antineoplastic/immunomodulating agents (aROR) for clozapine and structurally related drugs (loxapine, olanzapine and quetiapine) compared with other antipsychotic drugs. Cases were malignant lymphoma and leukaemia reports. Non-cases were all other reports including at least one antipsychotic report.

RESULTS

Of the 140 226 clozapine-associated reports, 493 were malignant lymphoma cases, and 275 were leukaemia cases. Clozapine was significantly associated with malignant lymphoma (aROR 9.14, 95% CI 7.75-10.77) and leukaemia (aROR 3.54, 95% CI 2.97-4.22). Patients suffering from those haematologic malignancies were significantly younger in the clozapine treatment group than patients treated with other medicines (p < 0.001). The median time to onset (available for 212 cases) was 5.1 years (IQR 2.2-9.9) for malignant lymphoma and 2.5 years (IQR 0.6-7.4) for leukaemia. The aROR by quartile of dose of clozapine in patients with haematologic malignancies suggested a dose-dependent association.

CONCLUSIONS

Clozapine was significantly associated with a pharmacovigilance signal of haematologic malignancies. The risk-benefit balance of clozapine should be carefully assessed in patients with risk factors of haematologic malignancies. Clozapine should be used at the lowest effective posology.

Gender disparities in clozapine prescription in a cohort of treatment-resistant schizophrenia in the South London and Maudsley case register

BACKGROUND

Gender disparities in treatment are apparent across many areas of healthcare. There has been little research into whether clozapine prescription, the first-line treatment for treatment-resistant schizophrenia (TRS), is affected by patient gender.

METHODS

This retrospective cohort study identified 2244 patients with TRS within the South London and Maudsley NHS Trust, by using a bespoke method validated against a gold-standard, manually coded, dataset of TRS cases. The outcome and exposures were identified from the free-text using natural language processing applications (including machine learning and rules-based approaches) and from information entered in structured fields. Multivariable logistic regression was carried out to calculate the odds ratios for clozapine prescription according to patients' gender, and adjusting for numerous potential confounders including sociodemographic, clinical (e.g., psychiatric comorbidities and substance use), neutropenia, functional factors (e.g., problems with occupation), and clinical monitoring.

RESULTS

Clozapine was prescribed to 77% of the women and 85% of the men with TRS. Women had reduced odds of being prescribed clozapine as compared to men after adjusting for all factors included in the present study (adjusted OR: 0.66; 95% CI 0.44-0.97; p = 0.037).

CONCLUSION

Women with TRS are less likely to be prescribed clozapine than men with TRS, even when considering the effects of multiple clinical and functional factors. This finding suggests there could be gender bias in clozapine prescription, which carries ramifications for the relatively poorer care of women with TRS regarding many outcomes such as increased hospitalisation, mortality, and poorer quality of life.

Clozapine prescribing: comparison of clozapine dosage and plasma levels between White British and Bangladeshi patients

AIMS AND METHOD

To compare differences in clozapine doses and plasma levels between Bangladeshi and White British patients. Following ethical approval we identified all current Bangladeshi and White British patients on clozapine maintenance in an east London clinic. We carried out univariate and multivariate regression analyses to examine associations between clozapine doses and ethnicity, age, gender, smoking status and weight. We also compared plasma clozapine levels of the two groups.

RESULTS

On univariate analysis White British patients had on average 85 mg higher doses than Bangladeshi patients (P = 0.004). Older age, male gender and smoking were also associated with higher dose. On multivariate analysis only age and smoking status remained significant. A greater proportion of Bangladeshi patients had high plasma clozapine levels compared with White British (30.76% v. 20.75%), although the difference was not statistically significant.

CLINICAL IMPLICATIONS

Our findings point to the need for the broadening of data collection on ethnic differences in clozapine prescribing within big data-sets such as Prescribing Observatory for Mental Health (POM-UK). Ethnopharmacological variations can inform more person-centred guidance on prescribing.

Ethnic minority inequalities in access to treatments for schizophrenia and schizoaffective disorders: findings from a nationally representative cross-sectional study

BACKGROUND

Ethnic minority service users with schizophrenia and schizoaffective disorders may experience inequalities in care. There have been no recent studies assessing access to evidence-based treatments for psychosis amongst the main ethnic minority groups in the UK.

METHODS

Data from nationally representative surveys from England and Wales, for 10,512 people with a clinical diagnosis of schizophrenia or schizoaffective disorders, were used for analyses. Multi-level multivariable logistic regression analyses were used to assess ethnic minority inequalities in access to pharmacological treatments, psychological interventions, shared decision making and care planning, taking into account a range of potential confounders.

RESULTS

Compared with white service users, black service users were more likely prescribed depot/injectable antipsychotics (odds ratio 1.56 (95% confidence interval 1.33-1.84)). Black service users with treatment resistance were less likely to be prescribed clozapine (odds ratio 0.56 (95% confidence interval 0.39-0.79)). All ethnic minority service users, except those of mixed ethnicity, were less likely to be offered cognitive behavioural therapy, compared to white service users. Black service users were less likely to have been offered family therapy, and Asian service users were less likely to have received copies of care plans (odds ratio 0.50 (95% confidence interval 0.33-0.76)), compared to white service users. There were no clinician-reported differences in shared decision making across each of the ethnic minority groups.

CONCLUSION

Relative to white service users, ethnic minority service users with psychosis were generally less likely to be offered a range of evidence-based treatments for psychosis, which included pharmacological and psychological interventions as well as involvement in care planning.

Informing progress towards race equality in mental healthcare: is routine data collection adequate?

The quality, completeness and coverage of ethnicity data in mental health services has long been regarded as unsatisfactory. The Department of Health's new 5-year action plan for delivering race equality in mental healthcare seeks to improve this key building block by setting out actions to improve both the quality of information and its analysis and dissemination. However, those that are tangible and specific are few: annual surveys of service users, national censuses of mental health in-patients and tables of National Confidential Inquiry suicide cases and in-patient deaths by ethnicity. The opportunity to seek improvements in the quality and coverage of key routine data-sets such as ethnic monitoring in primary care and the Hospital Episode Statistics database has not been seized. Moreover, the plan does not mention proposed changes in civil registration (births and deaths) and the coroner service and their potential benefit. The continuing gaps in the information base justify a stronger emphasis on the processes necessary to bring about change rather than on what ethnic monitoring should provide.

Does race affect prescribing for acute psychosis? Evaluation by a case vignette

BACKGROUND

Black people are over represented in mental health services and prescribing of antipsychotics differs by race in some countries. Our previous UK research into the prescribing of antipsychotics in large, multicentre studies found no important differences for black and white patients. However, we received several comments challenging our findings. We wanted to test the validity of these anecdotes by devising two case vignettes that differed only by race and asking prescribers to choose antipsychotic treatment.

METHOD

A case study was sent to all medical prescribers in the South London and Maudsley NHS Trust. Half of the prescribers for each grade of staff were sent the case study where the ethnicity of the patient was white and the other half where the ethnicity was black. Participants were asked to describe what they would prescribe for the patient. Outcomes were total percentage maximum dose, high dose, type of antipsychotic, route of administration and antipsychotic polypharmacy.

RESULTS

We received 123 completed case studies and demographic data forms from prescribers. There were no differences in percentage maximum dose, high dose, type, route and number of antipsychotics prescribed by case study ethnicity.

CONCLUSIONS

Prescribing for UK black and white patients is broadly similar when tested in clinical and theoretical studies.

Antipsychotic prescribing in Black and White hospitalised patients

Ethnicity may affect the prescribing of antipsychotic treatment. Previous UK studies conducted in south London have found few differences in antipsychotic prescribing quality for Black and White patients. This larger multicentre study examined the effect of ethnicity on antipsychotic prescribing quality in areas serving the largest proportions of Black patients in the UK. A cross-sectional survey with collection of multiple confounding factors potentially affecting outcomes in eight secondary care units in England over a three month period. Participants were Black or White inpatients prescribed regular antipsychotics on the day of the survey. Antipsychotic dose (expressed as a percentage of licensed maximum), high dose (being prescribed antipsychotic medication above maximum dose), polypharmacy (more than one antipsychotic prescribed), type (typical or atypical antipsychotic) and costs were the main outcome measures. Data were collected for 938 patients. There were no significant differences in any outcome by ethnicity: dose (adjusted percentage difference 0.97 [95% confidence interval (CI) -4.28, 6.22], p = 0.72); high dose (adjusted odds ratio (AOR) 0.98 [CI 0.63, 1.51], p = 0.92); polypharmacy prescribed (AOR 1.15 [CI 0.87, 1.51], p = 0.33); polypharmacy administered (AOR 1.08 [CI 0.78, 1.49], p = 0.66); use of typical antipsychotics (AOR 1.25 [CI 0.87, 1.79], p = 0.22); and cost (adjusted effect size 1.75 [CI -9.81, 13.31], p = 0.77). Antipsychotic prescribing practice did not differ between Black and White patients.

Ethnicity and psychopharmacology

Ethnicity is reported to be an important, but often ignored factor in psychopharmacology. However, recent advances in molecular biology and the vision of 'personalised medicine' have spurred a debate on the role of ethnicity in this field. This paper reviews literature on the role of race and ethnicity in psychopharmacology. Despite considerable controversy on what the concepts of ethnicity and race actually measure, they are considered as important proxies for a person's culture, diet, beliefs, health behaviours and societal attitudes. Research has shown ethnic differences in the clinical presentation, treatment, clinical response and outcome of mental illnesses. A number of ethnically specific variations have been found in the genetic and non-genetic mechanisms affecting pharmacokinetics and dynamics of psychotropic drugs, which might underlie the previously mentioned differences in drug use and response across ethnicities. Although some of these ethnic differences could be partially explained by genetic factors, a number of ethnically based variables like culture, diet and societal attitudes could potentially have a significant, but as yet unquantified influence as well. Future research needs to address the problems with defining and accurately measuring 'ethnicity', as well as focus upon conducting studies that could guide treatments for people from diverse backgrounds.

Antipsychotic prescribing quality and ethnicity: a study of hospitalized patients in south east London

A number of studies have shown qualitative and quantitative differences in prescribing of antipsychotics according to patient ethnicity. Black patients tend, for example, to be prescribed higher doses of antipsychotics than whites. Few studies have controlled for other factors which may influence prescribing practice and confound results. This study sought to determine whether or not ethnicity was associated with antipsychotic polypharmacy, high dosage and antipsychotic costs before and after adjustment for potential confounding. We approached inpatients on acute general psychiatry wards at the Maudsley, Bethlem and Lambeth hospitals in south east London. Prescription details were noted. Subjects were interviewed and social and clinical details were recorded. In all, data on 23 potential confounders were collected.A total of 210 patients were approached of whom 153 agreed to take part. Of the 23 potential confounders, only use of English as a first language and duration of illness differed significantly between blacks and whites. Categorical findings were adjusted for these factors and other potential confounders such as age and gender. Total antipsychotic daily dose was 82.2% of licensed maximum in blacks, and 77.2% in whites (p=0.48). Antipsychotic polypharmacy was seen in 23.2% of blacks and 16.9% of whites (adjusted odds ratio (OR) 1.11; 95% CI, 0.45-2.75). High dose (> 100% of maximum dose) antipsychotic regimens were prescribed to 15.9% of blacks and 16.9% of whites (adjusted OR, 0.71: 95% CI, 0.27-1.90). Mean monthly cost of treatment was significantly higher in blacks than whites (182.79 vs 143.08 British pound; p=0.02; adjusted OR (> 150 British pound/month), 2.45: 95% CI, 1.19-5.08). Prescribing quality was similar for blacks and whites. Black ethnicity was associated with significantly higher mean monthly medication costs.

A prescription survey of antipsychotic use in England and Wales following the introduction of NICE guidance

Objective : In the United Kingdom (UK) the National Institute for Clinical Excellence (NICE) has recommended the use of atypical antipsychotics for the treatment of schizophrenia. As part of its guidance it discourages the concurrent use of typical and atypical antipsychotics. In previous prescribing surveys antipsychotic polypharmacy has been noted to be widespread. We sought to evaluate atypical antipsychotic prescribing after the publication of NICE guidance. Method : We invited psychiatric centres in England and Wales to participate, in March 2004, in an atypical antipsychotic prescribing survey of hospital in-patients. Results : Thirty-six in-patient units submitted data for 2012 patients. After exclusions, 1092 patients were eligible. Of these, 28.6% (312) were prescribed a typical alongside an atypical antipsychotic and 19.3% (211) were prescribed high-dose antipsychotics. Co-prescription was more prevalent in patients aged 40 years and above (32.0 vs. 25.3%; P=0.018). It was also noted that in centres employing senior pharmacists, co-prescription was more common (28.6 vs. 14.3%; P=0.03). High-dose treatment was more commonly observed in patients of a white ethnic background (20.6 vs. 13.9%; P=0.02) as well as in patients aged 40 years and above (24.4 vs. 15.0%; P<0.001). Prescription of anticholinergics was significantly more prevalent in those receiving atypical and typical combinations than atypicals alone (26.0 vs. 12.0%; P<0.001). Conclusions : Antipsychotic polypharmacy remains commonplace. Similarly the prescription of high-dose antipsychotics is also widespread.